Remember when you were first learning to drive a car? You fumbled with the clutch, you killed it multiple times, lots of starts and stops. In my family when we were taught how to drive we used one of the older cars in our garage, that way if something happened the good cars wouldn't be damaged.
Learning to drive was very frustrating to me at first, I couldn't figure out how to operate the clutch and smoothly shift gears in a way that didn't jerk everyone around. I was very happy to learn in that 10 year old car, it made things much easier for me. The first time I drove my moms brand new Subaru WRX I nearly steered into the fence because I wasn't used to a car with such a sensitive gas pedal.
Imagine first learning to drive not in an old beater car, but a brand new Lamborghini! The idea of that might sound pretty cool, but for anyone that has driven a high performance car you know that everything about it means business. It accelerates blisteringly fast, it brakes are so powerful they can lock up even WITH anti-lock brakes. Definitely not a forgiving first car. To top that off you have to be extra careful so you don't scratch that crisp yellow paint job or bang your chromed dual exhaust on a speed bump.
Upping the Difficulty
Now take that example and add 2 things: Keeping 300+ pounds balanced on 2 wheels, and keeping the front end down. With a car you don't have to worry about balance at all, 4 wheels really helps with that, but with a motorcycle if you're going less than 5 mph you really need to watch your balance. Turning the motorcycle at all also requires balance, too much lean one way or another and you either end up on the pavement or wrapped around a telephone pole. Motorcycles have incredible acceleration and they require a lot of throttle control to operate properly. If you give a fast car too much gas all you are going to do is peel out, if you do that same thing on a motorcycle you could easily pull a wheelie and flip the bike. Most modern 600cc motorcycle are built for the race track, the only thing that makes them street legal is adding blinkers, headlights and a license plate. Even 500cc motorcycle will out accelerate all but the fastest cars in a quarter mile race, imagine what a 600cc, or a 1000cc motorcycle can do!
Do yourself a favor and when you get your first motorcycle buy something that is smaller than 600ccs, and preferable naked so you don't have to worry about scratching the fairings if you drop it in a parking lot. I was extremely careful and even I dropped my first motorcycle 2 times in the parking lot, and once at a stoplight (tuck in those laces while you ride or they will catch on your pegs!). It's definitely not an uncommon to hear of someone wrecking their brand new motorcycle less than a week after they leave the dealership. Not only will that hurt your pride, but it will also hurt your wallet and your body!